Trait mw_app::prelude::Debug

1.0.0 · source ·

pub trait Debug {
    // Required method
    fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>;
}

Expand description

? formatting.

Debug should format the output in a programmer-facing, debugging context.

Generally speaking, you should just derive a Debug implementation.

When used with the alternate format specifier #?, the output is pretty-printed.

For more information on formatters, see the module-level documentation.

This trait can be used with #[derive] if all fields implement Debug. When derived for structs, it will use the name of the struct, then {, then a comma-separated list of each field’s name and Debug value, then }. For enums, it will use the name of the variant and, if applicable, (, then the Debug values of the fields, then ).

Stability

Derived Debug formats are not stable, and so may change with future Rust versions. Additionally, Debug implementations of types provided by the standard library (std, core, alloc, etc.) are not stable, and may also change with future Rust versions.

Examples

Deriving an implementation:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

Manually implementing:

use std::fmt;

struct Point {
    x: i32,
    y: i32,
}

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Point")
         .field("x", &self.x)
         .field("y", &self.y)
         .finish()
    }
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:?}"), "The origin is: Point { x: 0, y: 0 }");

There are a number of helper methods on the Formatter struct to help you with manual implementations, such as debug_struct.

Types that do not wish to use the standard suite of debug representations provided by the Formatter trait (debug_struct, debug_tuple, debug_list, debug_set, debug_map) can do something totally custom by manually writing an arbitrary representation to the Formatter.

impl fmt::Debug for Point {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Point [{} {}]", self.x, self.y)
    }
}

Debug implementations using either derive or the debug builder API on Formatter support pretty-printing using the alternate flag: {:#?}.

Pretty-printing with #?:

#[derive(Debug)]
struct Point {
    x: i32,
    y: i32,
}

let origin = Point { x: 0, y: 0 };

assert_eq!(format!("The origin is: {origin:#?}"),
"The origin is: Point {
    x: 0,
    y: 0,
}");

Required Methods§

source

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

Examples

use std::fmt;

struct Position {
    longitude: f32,
    latitude: f32,
}

impl fmt::Debug for Position {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_tuple("")
         .field(&self.longitude)
         .field(&self.latitude)
         .finish()
    }
}

let position = Position { longitude: 1.987, latitude: 2.983 };
assert_eq!(format!("{position:?}"), "(1.987, 2.983)");

assert_eq!(format!("{position:#?}"), "(
    1.987,
    2.983,
)");

Trait mw_app::prelude::Debug

Stability

Examples

Required Methods§

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Examples

Implementors§

impl Debug for GlyphImageFormat

impl Debug for OutlineCurve

impl Debug for Action

impl Debug for accesskit::ActionData

impl Debug for AriaCurrent

impl Debug for CheckedState

impl Debug for DefaultActionVerb

impl Debug for DescriptionFrom

impl Debug for HasPopup

impl Debug for Invalid

impl Debug for ListStyle

impl Debug for Live

impl Debug for NameFrom

impl Debug for Orientation

impl Debug for Role

impl Debug for SortDirection

impl Debug for TextAlign

impl Debug for TextDecoration

impl Debug for accesskit::TextDirection

impl Debug for VerticalOffset

impl Debug for AhoCorasickKind

impl Debug for aho_corasick::packed::api::MatchKind

impl Debug for aho_corasick::util::error::MatchErrorKind

impl Debug for Candidate

impl Debug for aho_corasick::util::search::Anchored

impl Debug for aho_corasick::util::search::MatchKind

impl Debug for StartKind

impl Debug for ChmapPosition

impl Debug for ChmapType

impl Debug for ElemIface

impl Debug for ElemType

impl Debug for alsa::Direction

impl Debug for Round

impl Debug for ValueOr

impl Debug for SelemChannelId

impl Debug for alsa::pcm::Access

impl Debug for AudioTstampType

impl Debug for alsa::pcm::Format

impl Debug for alsa::pcm::State

impl Debug for TstampType

impl Debug for alsa::seq::EventType

impl Debug for LoadingError

impl Debug for async_channel::TryRecvError

impl Debug for ParseAlphabetError

impl Debug for base64::decode::DecodeError

impl Debug for base64::decode::DecodeError

impl Debug for DecodeSliceError

impl Debug for EncodeSliceError

impl Debug for DecodePaddingMode

impl Debug for CharacterSet

impl Debug for bevy_app::schedule_runner::RunMode

impl Debug for AssetServerError

impl Debug for HandleId

impl Debug for LoadState

impl Debug for AssetIoError

impl Debug for bevy_asset::io::metadata::FileType

impl Debug for PlaybackMode

impl Debug for Volume

impl Debug for ClearColorConfig

impl Debug for Camera3dDepthLoadOp

impl Debug for DebandDither

impl Debug for Tonemapping

impl Debug for StorageType

impl Debug for QueryEntityError

impl Debug for QuerySingleError

impl Debug for bevy_ecs::schedule::graph_utils::NodeId

impl Debug for LogLevel

impl Debug for ScheduleBuildError

impl Debug for QueryComponentError

impl Debug for GltfError

impl Debug for HierarchyEvent

impl Debug for bevy_input::ButtonState

impl Debug for AxisSettingsError